I haven't used stormycloud much but i haven't heard there being issues with them. I've preferred using outproxy.acetone.i2p and purokishi.i2p since i've found them consistently to be faster. Stormycloud is the default in vanilla i2p so they end up getting the brunt of i2p's outproxy traffic, it's possible they could get overloaded. They have a very good setup, but they're one entity.
Especially right now after mental outlaws video, more routers could be coming online and giving stormycloud a workout, maybe getting overwhelmed. I would try switching to either of those and setting inbound/outbound tunnel count to 16. hope that helps.