Well, it is very hard to monitor altcoins today especially when that altcoin is not popular or you haven't held any of it. If you are a hodler of altcoins for sure you will monitor it daily or weekly. Bitcoin has risen a large amount this month and of course, altcoins followed. But some of the altcoins right now increased by 200% to 300% after the rise of bitcoin so I believe alt coins had a bigger rise than BTC without checking the last year's chart.
Bitcoin is the mother coin of almost all of the token in the market that's why they are following what is the status of the btc and also depending on it.
It is not so difficult to monitor altcoins if you do not have over a hundred of them in your portfolio. As for their growth this May, Bitcoin showed better activity, which was a bit unusual. I guess, in June, alts will be faster.