My starter was doubling but it don’t do it anymore

After a week of 12 hours, 1:1:1 ratio feeding, I've reached a good growing starter, it doubles and falls as normal. But this last two days (day 9 and 10) it was rising but didnt reached double size. It may rise like 2/3 of its initial size after falling. In other hand I used part of this 1:1:1 starter sample to make a second sample but with more solid consistency (1:1:2 ratio) and its rising very well. So, I know starters can vary from sample to sample but I want to know if 2/3 rising its good as doubling or I have to change something?