RE:Jr. have been falling Not true. The GDXJ is adding 22 stocks and dropping none. The announcement was made on June 9th. Some are being reduced but I am not sure you can classify any of them as penny stocks. Any big moves are probably already priced in but if you feel lucky you can try to put in some stink bids.
You can download a spreadsheet here:
https://www.mvis-indices.com/reviews