i think not only about difficult, but also about the value, that was dumped on all altcoin, because of bitcoin chain split or hard fork, diff is indeed higher, because now even kids and their mother are mining, but the investors dumped a lot of money to take profit
The drop in profitability over the last month or so on almost all altcoins has been a LOT more about the rise in difficulty, though the drop in price has also had a noticeable negative effect.
Litecoin is the main exception, as it's price in $ terms has been pretty close to constant within a 10-15% range during that timeframe - so the profitability drop THERE has been all about the additional batches of L3+ and A4 miners getting added to the network hashrate.