What you are seeing is dissolved glue from the tape that lines the tank cavity and 100LL dye mixed together. Yes, there is a leak that needs to be fixed, but it might not be due to a hole in the bladder.
The first thing I encourage people to look at are all the attachment plates that bolt to the tanks. What are those? Inspection access panels and fuel transmitter locations. These places are usually installed with cork gaskets under the plates. Over time those gaskets crush, resulting in loss of torque on the bolts and, you guessed it, leaks. Re-torque all those panels. They have safety wired bolts and screws (on the transmitters). The transmitters seem to be especially prone to this, and may only leak when full of fuel and subjected to the highest internal pressure.
The other place there may be leak is in the vent system connections. The vent nipples on the outboard end of the tank will break causing a leak onlywhen the tank is filled to the brim.
I suspect many tanks are replaced and no longer leak because the above mentioned bolts get re-torqued during the process. If you still have leaks after doing this, you will at least have confirmation that the bladder does indeed need replacing. Bite the bullet then, not now.