Upside

pls help me with this:

scaredy cats who stick to bellweathers tech stocks are missing out on upside down the line.

can any one explain what is 'missing out on upside down the line'?

Thanks!

In the context of investments, "upside" means profit. "Down the line" means in the future. "Missing out on" means failing to get. The writer is saying that these investors will not make as much money sometime later as they would have made if they had chosen different stocks.