Slow faucet when water gets hot
It sounds to me like an overactive "scald prevention valve" - pretty much all USA faucets (and likely some other areas around the world) have been required for some time (certainly much more than 5 years) to have a mechanism that is designed to prevent scalding, so there's a thermally-active element in the faucet that is supposed to reduce flow when it's too hot. 

I would guess that yours is mal-adjusted (if adjustable) or simply failing in some way that makes it over-react long before it should. If you can find literature on your faucet (whether you actually saved it, or just can sort out the model and look it up with the manufacturer) you might discover if there is supposed to be some sort of adjustment. Depending on manufacturer there might also be a help or support number you can call (particularly among the "guaranteed for life" manufacturers.)