I agree with Tim's comments.
For reference, we have also used 4 blade hydromotives on our boat.
They are very sensitive if the engines are low in the water .. much better with the engines higher. They will definitely both put the bow down by default and bow steer if you trim right in on a turn. Trim tabs can help to correct this but are not essential.
Combination of trimming right in, your props, lots of water in the boat and a tight turn would cause the problem if you turned too tightly.
Worth setting your trim to level and then running the boat to see if you are still nose down. If so, a little cupping on the props will solve this. Then turns should be taken at level trim or slightly trimmed in from level, but not right in. If the engines are low, trim tabs will help also ... by default set level with the hull ... then adjust as Tim suggests if you can or if you have a co-driver... not essential tho.
You should then be able to take reasonable turns at speed ... we round bouys when racing at 60-70mph for 90degree turns ... not for u-turns obviously