yes, with lower BTC prices, most of the other altcoins will be followed, because the price of BTC is very influential in the market. with this decline it can be utilized as best as possible to start investing in the expected altcoin because of its affordable price. make sure the altcoin to be invested has a good development later by analyzing it first so you don't regret it later.
and the great time for start investing money in altcoin is when bitcoin price make correction after the price increased, because at this time many altcoin price are drop so deep and today bitcoin prie going down again, but i don't think bitcoin down stopped here, we still see there is a possibility that prices will go down