Hi Marko, I am have been doing the same process this past week. I ordered the Ischia and Camaldoli starters from sourdo.com. Last friday (April 05) I began to activate my Ischia culture. I haven't started the Camaldoli yet, but I did make my own proofing box with Ed Wood's directions in his Sourdough book. These are the first cultures I've ever activated.
I activated the Ischia culture in the proofer at 90 F for the first 24 hours and just like yours, it was very bubbly and active. I used the 1 qt wide mouth jars recommended and I remember the amount of volume increase was more than I expected. When I smelled mine after 24 hours I had what I believe to be a similar smell to yours. To me it smelled pleasant and fruity. Because I'm inexperienced in cultures I guess the smell is just my opinion and I could be wrong...
After the first step of mixing the dried packet of culture with flour and water, in Ed Wood's book, "Classic Sourdoughs" Ed writes, "Place the jar in a warm place (about 90 F) and proof for about 24 hours. . . This high starting temperature promotes the growth of lactobacilli and thus increases acid production. High acidity helps prevent contamination of the active culture by nonsourdough organisms present in most flour, most of which do not thrive in an acid environment. . . At the end of 24 hours, a few bubbles may appear in the culture as the first sign of growth and activity. Now reduce the proofing temperature to about 70 F. This lower temperature slows the bacterial growth and acid production - Important at this stage as too much acidity inhibits the growth of yeast. Continue feeding the culture every 12 to 24 hours for 3 to 5 days: feed 1 cup (140 grams) of flour and enough water (up to 3/4 cup/180ml) to maintain the thick pancake-batter consistency. It will be necessary to discard about half of the mixture before each feeding or the jar will over flow. Discarding dilutes the culture and helps reduce acid buildup. This is a good time to divide the culture into two jars - one for a backup in case of an accident with the other. . .Sometimes the culture becomes quite active in the first 24 hours. This could be a sign of contamination, but if the culture has a pleasant odor and continues to respond when fed, it is a good culture and can be retained. If the odor is unpleasant, follow the directions for washing a culture. . .(Classic Sourdoughs page 28-29).
Therefore the fruity smell did not concern me. After the first 24 hours, I dumped half of my culture out and fed it (I did not split it into two jars, a leap of faith I suppose). Then I fed it again about every 18 hours. After about 4 days I started to grow concerned that my culture was not activating because in Ed Wood's book he states, "When foam and bubbles increase the culture's volume by about 3 inches within 2 to 3 hours of its last feeding, the culture is fully active and can be used or refrigerated until needed (Classic Sourdoughs page 29).
After 4 days my culture was not increasing by that volume within 2 to 3 hours. So I switched to feeding it every 12 hours and on the 5th day It was fully active. The fruity smell was still there but not as strong and it doesn't smell foul to me. I then split the culture into two jars and put one in the fridge and the other one is still on my counter. I plan on making some pizza or at least hamburger buns with it this weekend. I'll let you know how it turns out.
I got Ed's book from the local library and it has more details than the instructions that came with the culture. I hope this helps