I would have a local spring shop provide you all new springs for each axle. Trailer manufacturers are known for providing the absolute minimum so if you load anything in the trailer or use it more than every few months, the springs will go bad. It's not a hard job - you just need lot's of jack stands and be very careful to stabilize everything. Looks like you need to add at least 1 leaf over your current springs, but bring your trailer weights to the spring shop and they can help you. Should cost no more than $400 for new springs, shackles, and bolts. Be sure and get the heavy-duty shackle kit - price is minimal and well worth the money.
