90g Electroless Copper Tinning PCB Tin Plating Crystals Immersion Preparation

HiFirst time using this brand and after adding the water etc as per instruction I attempted to tin a PCB. I would normally warm solutions to around 18 - 20C in a water bath before use and did the same here (ambient temp around 15C). Mixture was thoroughly dissolved and shaken prior to use.A small PCB (no more than 60 x 800mm) was put in a tray with solution. Upon contact the plating process began and it was left in solution for around ten minutes with the occasional gentle agitation. The PCB was then rinsed in hot/cold water. The finish was a very dull grey at best that could be removed with alcohol wipes.The solution (in bottle) has now turned a brown colour (never seen that before).Admittedly I didn't use the whole solution in the process, just enough to cover the PCB by a bit, but I've never had much issue this way before. The PCB had been cleaned prior to plating.I will try it again, using the entire contents to see if that makes a difference and if so I will update my review.